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IAN Research Findings: Regression

June 24, 2008

The Interactive Autism Network (IAN), a project collecting information online from families of children with autism spectrum disorders (ASDs) from throughout the United States, reports on developmental regression in autism. What does current research say about loss of language, social, motor, or living skills in children with ASDs? How many families participating in the IAN Project report that their child experienced such a loss?

Please Note: These Findings Are Preliminary
The analyses presented here by the Interactive Autism Network are preliminary. They are based on information submitted via the Internet by parents of children with autism spectrum disorders (ASDs) from the United States who choose to participate. The data have not been peer-reviewed -- that is, undergone evaluation by researchers expert in a particular field -- or been submitted for publication. IAN views participating families as research partners, and shares such preliminary information to thank them and demonstrate the importance of their ongoing involvement.

We encourage autism researchers investigating these topics to apply for access to the IAN database. Contact

Regression in Autism Spectrum Disorders

The term regression refers to a loss of previously acquired skills, such as language, motor, or life skills. Although not all children with ASDs experience such a loss, it has been documented that a substantial number of them do, especially in the realm of language.[1] [2] In fact, a child's loss of previously acquired words has been described as a “useful red flag for ASD in a significant minority of cases.” [3]

Researcher Sally Rogers of the U.C. Davis M.I.N.D. Institute describes three patterns of autism onset:[4]

  1. No period of typical development -- autism symptoms present from birth
  2. Developmental plateau -- child begins to reach developmental milestones and then stops acquiring new skills
  3. Regression -- child loses skills

How many children with ASD experience regression has been the focus of much recent research, as has the question of how many develop normally (or do not) prior to such a loss of skills. One study of 351 children with ASD found that 46% were reported to have regressed.[5] The majority of those who experienced regression had not developed typically prior to losing skills, exhibiting what has been called “the delays-plus-regression phenotype.”[6] Another study found that 41% of children had lost language skills, social skills, or both.[7] A third, using a very strict definition of regression, reported only 11.8% of children with autism, and 5.5% of children with other ASDs, had experienced a “clear or possible” loss of skills.[8]

Interactive Autism Network: What Do IAN Families Report About Regression?

IAN is collecting information via the Internet from thousands of families of children with ASD throughout the United States. What have these families been reporting about regression in their children with ASD? Does the information they are sharing confirm, refute, or expand upon what other researchers have found?

The following questions were asked:

  1. Did your child lose words, daily living skills, motor abilities, or social skills that he/she previously had?
  2. How significant was your child's loss of skills?
  3. Which type of skill was affected most (speech and language, motor abilities, social skills, or daily living skills)?
  4. What age was your child when you first noticed this loss of skills?
  5. Did your child's development plateau or halt such that he/she stopped gaining new skills but retained previously acquired skills?
  6. What age was your child when you first noticed this plateau or halt in his/her development?

Researchers investigating autism-related regression are careful to define exactly what constitutes regression and have strict criteria for determining whether such regression is linked to autism and not to something else. (However, the definition of regression may vary from study to study.) Typically, researchers use a combination of clinical observation and parent-report to confirm that autism-related regression occurred.

In contrast, IAN's information is based on parent-report only. It should also be noted that we did not ask: "Did your child experience autism-related regression?" We asked about skill loss and plateaus. This made our questions more family-friendly, but also means that types of skill loss that do not represent autism-related regression may have been reported. For example, there are parents who indicated that their child lost skills after a major emotional trauma; this can occur with typically developing children, too, and would probably not be considered autism-related. Still, most IAN parents reporting skill loss and developmental plateaus described them occurring in children under age three, and in the communication domain. This is a good indication that the questions above did capture autism-related regression in most cases.


We began by looking at children who had been reported to lose skills, and the age at which they had done so. It soon became clear that, no matter the specific ASD diagnosis, the majority of them had lost skills between 13 and 18 months of age. (See Figure 1.) Even some children with Asperger's syndrome -- a diagnosis not commonly associated with regression-- were reported to have lost skills by IAN parents.

Figure 1.

Note: ASD (Autism Spectrum Disorder) and PDD (Pervasive Developmental Disorder) are “catch-all” diagnostic categories sometimes used as a preliminary diagnosis. These are often later replaced by more specific diagnoses, such as Autism or Asperger's syndrome.

As we examined our data, we realized that some parents were reporting skill loss taking place well after their child reached 36 months of age. According to the Diagnostic and Statistical Manual of Mental Disorders, fourth edition (DSM IV), children with an autism diagnosis are supposed to have shown symptoms before age 36 months.

[9] In the literature, furthermore, regression has been most frequently reported to take place during the toddler years. To understand what type of skill loss parents were reporting in older children, we turned to the comments that parents are able to leave for researchers when they fill in the IAN questionnaires.

From parents' comments, it appears that this late skill loss is something very different from what is typically thought of as “regression.” It does not generally involve language loss, but losses in social functioning. Some parents reported the increasing distress that can impact higher-functioning children on the spectrum when their peers' social development begins to outstrip their own. Unfortunately, this was perhaps not so much about a loss of skills as about a growing realization of difference, a loss of self-esteem, and the struggles that accompany this:

  • “He went from being cheerful and full of smiles to being sarcastic and sullen to others.” –of a child with PDD-NOS who had difficulty at age 5
  • “Lost social skills, or his anxiety over social failure increased to the point he no longer had the confidence he once had had.” –of a child with Asperger's who had difficulty at age 6
  • “My son has lost social skills and the ability to cope with stress. He used to be very social and always had friends. He now has very low self-esteem, is very negative, and does not make friends easily.” –of a child with Asperger's who had difficulty at age 9

These losses and struggles of older children are an important topic in their own right. They do not truly represent regression as defined by most researchers, however. In order to compare our figures for regression with those of other researchers, we decided to focus only on skill loss reported at 36 months of age or earlier. That way, we would avoid mixing regression with other varieties of loss experienced by older children. (See Figure 2.)

Figure 2.

IAN data confirm that nearly half of children with a diagnosis of autism experience regression before age 3. Children with other autism spectrum diagnoses also experience regression, although to a lesser degree. (See Table 1.)

Table 1. Regression by ASD Diagnosis

Autism Spectrum Diagnosis

Number of Children with Skill Loss 0-36 months

Percentage of Children with Skill Loss
0-36 months

Autism (n=2622)



PDD-NOS (n=1220)



ASD (n=524)



Asperger's syndrome (n=973)



PDD (n=174)



All (n=5513)



Parents of children with autism were the most likely to describe the regression as severe, and the majority of parents of children with other diagnoses rated the regression as moderate. (See Figure 3.)

Figure 3.

As would be expected from previous research, language was the skill most frequently identified as “affected most” for all children on the spectrum, followed by social skills. Even some children with Asperger's syndrome, who supposedly do not experience speech delays, were reported to have lost speech or language skills. (See Table 2.)

Table 2. Of Those Who Were Reported to Have Regressed,
Lost Skill That Was Affected Most: Autism, PDD-NOS, Asperger's



Asperger's Syndrome





Social Skills
(like eye contact and playing with other children)




Motor Abilities
(like walking, jumping, and playing with small toys)




Daily Living Skills
(like feeding oneself and toileting)




Table 2 shows only what skill was affected most, and does not address the question of whether multiple skills were affected. A number of parents wrote in the comments section that all these skills were affected at the same time, so it was difficult to choose among them.

Developmental Plateaus

Some families did not report out-and-out regression, but a developmental plateau – one of the types of autism onset described by Rogers. How common was this among IAN families?

Developmental stagnation was reported far less often than loss of skills, but it was definitely reported. More than 900 children were reported to have reached a developmental plateau, with nearly 800 experiencing such a plateau at age 36 months or younger.

Would the age at which children reached a developmental plateau be the same or different from the age at which children were reported to regress? Based on the IAN data, it appears that the typical age for regression and developmental plateau is similar. Just as for regression, the most typical age for a reported developmental plateau was between 13 and 18 months of age.

Looking at loss and stagnation of skills together we found that of the 5,472 children whose parents answered the “lost skills” or “plateau” questions, and who were age 3 or younger when a loss or stagnation of skills occurred, 2,502 (46%) experienced neither a developmental regression nor plateau; 2,114 (39%) experienced regression; and 856 (15%) experienced a plateau. (See Table 3.)

Table 3. Regression vs. Plateau

Child's Status

Number of Children

(<= 36 mos. of Age)

Percentage of Children

(<= 36 mos. of Age)

Neither Regression nor Plateau



Regression Only



Plateau Only



Total with Regression or Plateau






All together, 54% of the children with ASD participating in IAN have been affected by some kind of loss or stagnation of skills by age 3. As we have seen, this varies to some degree by ASD diagnosis. (See Figure 4.)

Figure 4

In Conclusion

According to the reports of IAN families, 39% of children with a variety of ASDs, and 49% of children with a diagnosis of autism, experience a loss of skills by age 3. These figures are in the same range as those reported by at least two other studies (46%[10]; 41%[11]), but higher than those reported in a study at Yale using a very strict definition of regression.[12]

IAN's data also demonstrate the importance of including numbers on children who experience a developmental plateau such that they stop gaining skills without actually losing any. Fifteen percent of children participating in IAN were reported to have hit such a developmental plateau, which brings the total number of children experiencing a developmental loss or halt to 54%.

IAN's findings also confirm the type of skills that are most frequently lost. No matter the ASD diagnosis, speech and language was the skill area reported as “most affected,” followed by social skills. As in other studies, a small number of families reported loss of daily living skills or motor skills.

As we examine all the information we have on skill loss or stagnation, it becomes clear how important it is for those studying these issues to precisely define what constitutes a regression or plateau. Do losses in only certain skill categories count? Should children with Asperger's be included in studying the phenomenon, or does their participation “wash down” the numbers? (In our study, children with Asperger's were far less likely to regress than children with other ASD diagnoses.) Should only certain age categories be considered? And if there are losses of some type occurring at later ages, how should these be characterized and studied? It is our hope that the IAN data on developmental regression and plateaus – currently based on the experience of more than 5,000 children with ASD – will help researchers answer these and other questions.

To Share Your Thoughts About These Findings…

If you have comments and insights about these preliminary findings, please share them in the research-focused IAN Community Discussion Forum. Your feedback may influence future research.

(Any member of the public may view these discussions, but to post you must join IAN Community. Go to IAN Community and click “JOIN NOW.”)

What is IAN?
The primary goal of the Interactive Autism Network (IAN) is to accelerate the pace of autism research. Families affected by autism answer questionnaires over the internet, from the comfort of home. Researchers apply to IAN to use the resulting data, or to find participants for their local studies. The IAN Community, meanwhile, provides evidence-based basic information on Autism Spectrum Disorders, articles by leading researchers in the field, and reports on IAN's latest findings.

To learn more about the IAN Project, please go to
To join the IAN research project, please go to


[1] Werner, E., & Dawson, G. (2005). Validation of the phenomenon of autistic regression using home videotapes. Archives of General Psychiatry, 62(8), 889-895.
[2] Goldberg, W. A., Thorsen, K. L., Osann, K., & Spence, M. A. (2008). Use of home videotapes to confirm parental reports of regression in autism. Journal of Autism and Developmental Disorders,38(6), 1136-1146.
[3] Lord, C., Shulman, C., & DiLavore, P. (2004). Regression and word loss in autistic spectrum disorders. Journal of child psychology and psychiatry, and allied disciplines, 45(5), 936-955.
[4] Rogers, S. J. (2004). Developmental regression in autism spectrum disorders. Mental retardation and developmental disabilities research reviews, 10(2), 139-143.
[5] Richler, J., Luyster, R., Risi, S., Hsu, W. L., Dawson, G., Bernier, R., et al. (2006). Is there a 'regressive phenotype' of autism spectrum disorder associated with the measles-mumps-rubella vaccine? A CPEA study. Journal of Autism and Developmental Disorders, 36(3), 299-316.
[6] Ozonoff, S., Williams, B. J., & Landa, R. (2005). Parental report of the early development of children with regressive autism: The delays-plus-regression phenotype. Autism : the international journal of research and practice, 9(5), 461-486.
[7] Hansen, R. L., Ozonoff, S., Krakowiak, P., Angkustsiri, K., Jones, C., Deprey, L. J., et al. (2008). Regression in autism: Prevalence and associated factors in the CHARGE study. Ambulatory pediatrics : the official journal of the Ambulatory Pediatric Association, 8(1), 25-31.
[8] Siperstein, R., & Volkmar, F. (2004). Brief report: Parental reporting of regression in children with pervasive developmental disorders. Journal of Autism and Developmental Disorders, 34(6), 731-734.
[9]American Psychiatric Association. (2000). Diagnostic and statistical manual of mental disorders (DSM-IV-TR) (4th ed., text revision ed.). Washington, DC: American Psychiatric Association.
[10] Richler, J., Luyster, R., Risi, S., Hsu, W. L., Dawson, G., Bernier, R., et al. (2006). Is there a 'regressive phenotype' of autism spectrum disorder associated with the measles-mumps-rubella vaccine? A CPEA study. Journal of Autism and Developmental Disorders, 36(3), 299-316.
[11] Hansen, R. L., Ozonoff, S., Krakowiak, P., Angkustsiri, K., Jones, C., Deprey, L. J., et al. (2008). Regression in autism: Prevalence and associated factors in the CHARGE study. Ambulatory pediatrics : the official journal of the Ambulatory Pediatric Association, 8(1), 25-31.
[12] Siperstein, R., & Volkmar, F. (2004). Brief report: Parental reporting of regression in children with pervasive developmental disorders. Journal of Autism and Developmental Disorders, 34(6), 731-734.